In recognition of the significant expenses associated with hydrocarbon wells, added emphasis has been placed on well logging, profiling and monitoring of conditions throughout the life of a well. As a result, the detecting, monitoring and intervention of well conditions over the years has become a more sophisticated and critical part of managing well operations.
Initial gathering of information relative to well and surrounding formation conditions may be obtained by way of a logging or monitoring application. That is, equipment at the surface of an oilfield adjacent to the well may be used to deploy a logging tool with various sensors embedded within it in the well. Often, an electrically conductive logging cable is used to deliver the logging tool into the well. The logging cable may include a variety of power and communicative lines incorporated into the cable may be of relatively substantial weight, strength, and profile. Thus, the cable may be well suited for delivery of the logging tool to significant well depths without undue concern over the accommodated load of the tool or perhaps the increasing load of the cable itself.
In order to reduce the overall weight of the cable, communicative functionality may be provided to the cable by incorporation of a single or multi-channel fiber optic line. Indeed, given the high speed data transmission achievable through conventional fiber optic line, its incorporation into the cable theoretically provides substantially high data bandwidth rate for real-time communicative capacity to operations employing the cable.
Unfortunately, however, the above described cable is managed at the oilfield surface through a drum, winch or other conventional winding device. That is, at surface, the cable is wound and unwound from a rotating drum in order to position a tool such as the noted logging tool in the well. As a result, light transmissible data that is communicated over the fiber optic line from the tool is typically only collected at a data storage device associated with the rotatable drum or other rotating management tool. Once such data is collected, the drum may be stopped and the data transferred from the data storage device to a stationary processor for analysis. This initial stopping of the drum rotation is due to the fact that the physical challenges of collecting light transmitted data from a moving drum device are viewed as cumbersome and impractical. Unlike electrical communications, where a rotating disk and contact slip-ring configuration would allow for transmission from moving to non-moving structures, such is not available in the case of oilfield light transmissions, particularly of the multi-channel variety above, it's high speed, real-time benefits generally go unrealized. That is, readings are taken by a downhole sensor of the logging tool. These readings are transmitted uphole at near real-time speeds only to be stored at the storage device for a period of time. Rotation of the drum is eventually halted, and, finally, data from the now still device is downloaded for analysis. Thus, as a practical matter, no high speed real-time communication benefits are realized.
It has been suggested that data may be acquired in a manner that obviates physical challenges associated with the combination of light transmissions and a rotating drum. For example, in theory, the light data may be collected and converted into a wireless signal at the rotating drum. Thus, wireless collection of the signal data from the drum would not require that the rotation of the drum be halted. As a result, the signal data could be immediately transmitted to a stationary processor at the oilfield surface for analysis. In this manner, the high speed nature of the fiber optic line may be taken advantage of.
Unfortunately, at the oilfield, applications such as the noted logging and intervention application, are often run in conjunction with a host of others. Many of these other applications involve the use of explosives, such as in the case of perforating a sub surface formation, a common application run in conjunction with logging. Therefore, as a matter of safety, devices prone to generate static or electro-magnetic interference are avoided. Unfortunately, this includes devices such as those employed for wireless transmissions. As a result, while fiber optic line is often utilized as a means to reduce cable weight, its real-time high-speed potential and advantages of very high volume data transmission capabilities remain largely unrealized at the oilfield.